Nano-reactions at solid surfaces by an atomic force microscope with a molecular-recognition cantilever

1.利用原子力显微镜，我们试图在纳米尺度上控制光化学反应。在紫外光照射下，施加10 V的正电压，在TiO_2表面选择性地加速了硬脂酸薄膜的光催化分解。的光催化分解的空间分辨率估计为30 nm或更小的硬脂酸膜的图案。AFM辅助的光致发光可以用外加电场在TiO_2表面光生空穴的积累来解释。结果表明，AFM辅助的氧化反应适用于纳米尺度的有机物氧化反应.我们开发了一种新的技术来转录由AFM辅助光刻产生的纳米图案。采用射频溅射法在室温下制备了TiO_2，SnO_2，Nb_2O_5，Ga_2O_3光催化薄膜。这些氧化物膜是具有平坦表面的非晶的。特别是， ...更多信息 在2 × 10 ~（-3）Torr高压下制备的TiO_2薄膜<-2>具有最高的光催化活性。结果表明，非晶态TiO_2薄膜具有与晶态TiO_2薄膜相当的光催化性能。这种高的光催化活性可能是由于TiO_2纳米晶的形成。非晶态TiO_2薄膜与Si基片上的辛基三氯硅烷（OTS）自组装膜接触后，在5 min内完全分解为CO_2和H_2O，在30 s内部分转化为OTS自组装膜，但不清晰。实现光催化光刻需要抑制反应物种的横向扩散.十二烷基硫醇和氨基硫酚的自组装膜形成在涂覆有Au的悬臂梁上。测量了Au衬底和这些用SAM修饰的电极之间的电流-电压特性。在十二烷基硫醇和氨基硫酚自组装膜之间发现了电流与电压特性的巨大差异：氨基硫酚自组装膜在小偏压下有不同的电流。在复阻抗图中，在小于5 Hz的频率下，氨基硫酚自组装膜引起阻抗的小真实的部分对应于交流电导。将含有60个碱基的单链DNA固定在沉积在Au基底上的氨基硫酚自组装膜上。在AFM形貌图中，由于DNA的聚合，存在大量的DNA网络。修饰的悬臂梁与aminophiophiophenol自组装膜导致没有意义的地图的交流电导率相对于DNA网络。主要原因是交流电导率的响应时间太长，无法在100 nm x 100 nm的区域内绘制地图。少

1. Using an atomic force microscope, we attempted to control the photochemical reactions in nanometer-scale. The photocatalytic decomposition of the stearic-acid film was selectively accelerated at the TiO_2surface where a positive voltage of 10 V was applied under ultraviolet illumination. The spatial resolution of the photocatalytic decomposition was estimated to be 30 nm or less from patterns of stearic-acid films. The AFM-assisted photocatalysis can be explained in terms of the accumulation of photogenerated holes at the TiO_2 surface by applying an electric field. It was found that the AFM-assisted photocatalysis was applicable to oxidation reactions of organic compounds in nano-meter scale.2. We developed a new technique to transcribe nano-patterns produced by AFM assisted lithography. The photocatalysts films of TiO_2, SnO_2, Nb_2O_5, Ga_2O_3 were prepared at room temperature by a RF sputtering technique. These oxide films are amorphous with flat surfaces. In particular, amorpho … More us TiO_2 films prepared at a higher pressure of 2x10^<-2> Torr exhibited the highest photocatalytic activity in these oxide films. We demonstrated that these amorphous TiO_2 films have the photocatalytic ability comparable to that of crystalline one. The high photocatalytic activity may be ascribed to the formation of nano-crystals of TiO_2. The amorphous TiO_2 films, which are in contact with self-assembled membranes of octyl-trichlorosilane (OTS) deposited on Si wafers, decomposed completely OTS films into CO_2 and H_2O within 5 min. The patterns of TiO_2 films were transcribed in part to OTS-SAMs within 30 s, but the resultant patterns are unclear. The suppression of lateral diffusion of reactive species are required to realize photocatalytic lithography.3. SAMs of dodecanethiol and aminothiophenol are formed on cantilevers coated with Au. Current vs. voltage characteristics were measured between Au substrates and these cantilevers modified with SAMs. Drastic differences in current vs. voltage characteristics were found between dodecanethiol and aminothiophenol SAMs: distinct current flow at a small bias voltage for aminothiophenol SAMs. In complex impedance plots, the aminothiophenol SAMs gave rise to small real part of impedance corresponding ac conductance at a frequency less than 5 Hz. Single strand DNA with 60 bases was immobilized to aminothiophenol SAMs deposited on Au substrate. In AFM topographs, there were a large number of networks of DNA because of its polymerization. The cantilever modified with aminophiophenol SAMs leads to no meaningful maps of ac conductivity with respect to the DNA networks. Major reason is the response time of the ac conductivity is too long to draw the map in area of 100 nm x 100 nm. Less